package org.apache.solr.spelling;

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.Token;
import org.apache.lucene.search.spell.StringDistance;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.core.SolrCore;
import org.apache.solr.handler.component.SpellCheckMergeData;
import org.apache.solr.search.SolrIndexSearcher;

/**
 * <p>
 * This class lets a query be run through multiple spell checkers. The initial
 * use-case is to use {@link WordBreakSolrSpellChecker} in conjunction with a
 * "standard" spell checker (such as {@link DirectSolrSpellChecker}
 * </p>
 */
public class ConjunctionSolrSpellChecker extends SolrSpellChecker {
	private StringDistance stringDistance = null;
	private Float accuracy = null;
	private String dictionaryName = null;
	private Analyzer queryAnalyzer = null;
	private List<SolrSpellChecker> checkers = new ArrayList<SolrSpellChecker>();
	private boolean initalized = false;

	public void addChecker(SolrSpellChecker checker) {
		if (initalized) {
			throw new IllegalStateException(
					"Need to add checkers before calling init()");
		}
		try {
			if (stringDistance == null) {
				stringDistance = checker.getStringDistance();
			} else if (stringDistance != checker.getStringDistance()) {
				throw new IllegalArgumentException(
						"All checkers need to use the same StringDistance.");
			}
		} catch (UnsupportedOperationException uoe) {
			// ignore
		}
		try {
			if (accuracy == null) {
				accuracy = checker.getAccuracy();
			} else if (accuracy != checker.getAccuracy()) {
				throw new IllegalArgumentException(
						"All checkers need to use the same Accuracy.");
			}
		} catch (UnsupportedOperationException uoe) {
			// ignore
		}
		if (queryAnalyzer == null) {
			queryAnalyzer = checker.getQueryAnalyzer();
		} else if (queryAnalyzer != checker.getQueryAnalyzer()) {
			throw new IllegalArgumentException(
					"All checkers need to use the same Analyzer.");
		}
		checkers.add(checker);
	}

	@SuppressWarnings("unchecked")
	@Override
	public String init(NamedList config, SolrCore core) {
		for (int i = 0; i < checkers.size(); i++) {
			SolrSpellChecker c = checkers.get(i);
			String dn = c.init(config, core);

			// TODO: in the future, we could develop this further to allow
			// multiple spellcheckers with per-field dictionaries...
			if (dictionaryName != null && !dictionaryName.equals(dn)) {
				throw new IllegalArgumentException(
						"Cannot have more than one dictionary. (" + dn + " , "
								+ dictionaryName + ")");
			}
			dictionaryName = dn;
		}
		if (dictionaryName == null) {
			dictionaryName = DEFAULT_DICTIONARY_NAME;
		}
		initalized = true;
		return dictionaryName;
	}

	@Override
	public void build(SolrCore core, SolrIndexSearcher searcher)
			throws IOException {
		for (SolrSpellChecker c : checkers) {
			c.build(core, searcher);
		}
	}

	@Override
	public SpellingResult getSuggestions(SpellingOptions options)
			throws IOException {
		SpellingResult[] results = new SpellingResult[checkers.size()];
		for (int i = 0; i < checkers.size(); i++) {
			results[i] = checkers.get(i).getSuggestions(options);
		}
		return mergeCheckers(results, options.count);
	}

	@Override
	public SpellingResult mergeSuggestions(SpellCheckMergeData mergeData,
			int numSug, int count, boolean extendedResults) {
		SpellingResult[] results = new SpellingResult[checkers.size()];
		for (int i = 0; i < checkers.size(); i++) {
			results[i] = checkers.get(i).mergeSuggestions(mergeData, numSug,
					count, extendedResults);
		}
		return mergeCheckers(results, numSug);
	}

	// TODO: This just interleaves the results. In the future, we might want to
	// let users give each checker its
	// own weight and use that in combination to score & frequency to sort the
	// results ?
	private SpellingResult mergeCheckers(SpellingResult[] results, int numSug) {
		Map<Token, Integer> combinedTokenFrequency = new HashMap<Token, Integer>();
		Map<Token, List<LinkedHashMap<String, Integer>>> allSuggestions = new LinkedHashMap<Token, List<LinkedHashMap<String, Integer>>>();
		for (SpellingResult result : results) {
			if (result.getTokenFrequency() != null) {
				combinedTokenFrequency.putAll(result.getTokenFrequency());
			}
			for (Map.Entry<Token, LinkedHashMap<String, Integer>> entry : result
					.getSuggestions().entrySet()) {
				List<LinkedHashMap<String, Integer>> allForThisToken = allSuggestions
						.get(entry.getKey());
				if (allForThisToken == null) {
					allForThisToken = new ArrayList<LinkedHashMap<String, Integer>>();
					allSuggestions.put(entry.getKey(), allForThisToken);
				}
				allForThisToken.add(entry.getValue());
			}
		}
		SpellingResult combinedResult = new SpellingResult();
		for (Map.Entry<Token, List<LinkedHashMap<String, Integer>>> entry : allSuggestions
				.entrySet()) {
			Token original = entry.getKey();
			List<Iterator<Map.Entry<String, Integer>>> corrIters = new ArrayList<Iterator<Map.Entry<String, Integer>>>(
					entry.getValue().size());
			for (LinkedHashMap<String, Integer> corrections : entry.getValue()) {
				corrIters.add(corrections.entrySet().iterator());
			}
			int numberAdded = 0;
			while (numberAdded < numSug) {
				boolean anyData = false;
				for (Iterator<Map.Entry<String, Integer>> iter : corrIters) {
					if (iter.hasNext()) {
						anyData = true;
						Map.Entry<String, Integer> corr = iter.next();
						combinedResult.add(original, corr.getKey(),
								corr.getValue());
						Integer tokenFrequency = combinedTokenFrequency
								.get(original);
						if (tokenFrequency != null) {
							combinedResult.addFrequency(original,
									tokenFrequency);
						}
						if (++numberAdded == numSug) {
							break;
						}
					}
				}
				if (!anyData) {
					break;
				}
			}
		}
		return combinedResult;
	}

	@Override
	public void reload(SolrCore core, SolrIndexSearcher searcher)
			throws IOException {
		for (SolrSpellChecker c : checkers) {
			c.reload(core, searcher);
		}
	}

	@Override
	public Analyzer getQueryAnalyzer() {
		return queryAnalyzer;
	}

	@Override
	public String getDictionaryName() {
		return dictionaryName;
	}

	@Override
	protected float getAccuracy() {
		if (accuracy == null) {
			return super.getAccuracy();
		}
		return accuracy;
	}

	@Override
	protected StringDistance getStringDistance() {
		if (stringDistance == null) {
			return super.getStringDistance();
		}
		return stringDistance;
	}

	@Override
	public boolean isSuggestionsMayOverlap() {
		return true;
	}
}
